1. Field of the Invention
The present invention relates to an optical system, and in particular to a multi optical-route Head Up Display (HUD) suitable for use in a moving vehicle.
2. The Prior Arts
Head Up Display (HUD) is an auxiliary aviation instrument that was first utilized in an aircraft, so that a pilot is able to look at the information on the panel without lowering his head, to avoid interruption of attention and lose control of Situation Awareness. The Head Up Display (HUD) can not only provide convenience in usage, but it can also raise the aviation safety. Therefore, it can be used in any of the moving vehicles, such as aircrafts, or even automobiles and ships.
In the past, the Head Up Display of the prior art provided only a small display area of simple instrument information within the eyesight of the driver, such as, vehicle operation temperature, engine rotation speed, vehicle driving speed, or a few guidance reminders having small arrow heads. Nowadays, with the progress of science and technology, the driver may have other multiple choices; wherein, the Head Up Display (HUD) is able to display tire pressure, gear shift reminder, turning-around & back-up reminder, obstacle warning, flying attitude, flying speed, flying direction, vertical speed variations, aircraft inclination angle, wind direction, or other information about the moving-forward or slow-down of the moving vehicle. However, presently on market, any of the Head Up Display belongs to a single optical-route display device, thus it is not easy to integrate the single optical-route display device and an instrument panel into an integral unit, since the volume required by the Head Up Display is overly large for the panel full of wires and various connections. Also, according to the optical and imaging principles, for any lens or mirror, the area required for input image and image formations is positively proportional to the size of optical elements of the lens and mirrors. Furthermore, in order to keep the quality of imaging, the size of optical element used for a Head Up Display can not be reduce further, therefore, it is rather difficult to achieve large display area in a very limited space of the driver cabin. Also, for information displayed in an overly small display area, the driver is not able to obtain critical and important information right away by glancing briefly over instrument control panel; or in case that the driver does raise his head to look at and get the critical information on the display panel in detail, that could disrupt his attention and put him in an immediate danger.
Therefore, presently, the design and performance of the Head Up Display (HUD) is not quite satisfactory, and it has much room for improvements.